Abstract Menisci play critical roles in stabilization and load transmission in the knee joint. Meniscal damage or loss often results in progressive osteoarthritic degeneration of the articular cartilage and other joint tissues, leading to significant pain and disability. We need better methods to repair or replace damaged menisci. However, most tissue engineering approaches for meniscal replacement require significant culture time for the newly formed tissue to develop functional properties that could withstand joint loading. We have demonstrated the usefulness of three dimensional (3-D) woven scaffolds for tissue engineering purposes. These scaffolds provide physiologic mechanical properties prior to implantation. We have also shown that mechanical stress and cytokines alter the metabolism of menisci and inhibit repair of meniscal injury. The overall goal of our study is to develop a new 3-D composite scaffold for use in the functional tissue engineering of the meniscus. A special advantage of 3-D weaving is that constructs can be designed and built with predetermined control of site-dependent variations in mechanical properties. Also, certain growth factors that may enhance meniscus-bone molding and annealing can be incorporated into the matrix. We will develop the device and also determine effects of soluble mediators such as cytokines, nitric oxide (NO), and prostaglandins (PG) on development, integrity, and function of the prostheses. We will accomplish 4 aims. Aim 1. Design and construct 3-D woven composite scaffolds for use in the functional tissue engineering of the knee meniscus. We will develop a composite scaffold that promotes meniscal fibrochondrocyte development and tissue organization, while effectively replicating the structural and functional mechanical properties of a natural meniscus. Aim 2: Incorporate bioactive factors into the 3-D matrix that will allow fibrochondrocyte differentiation and attachment to bone. We will incorporate growth factors into the materials used in Aim 1 to construct the 3-D woven composite scaffolds. Aim 3: Perform mechanical testing of the composite scaffolds to assess their potential in vitro functionality. Tension, compression, and shear testing will be used to evaluate the critical biomechanical parameters of the developed scaffolds and resulting neomeniscus. We will assess the importance of certain cytokines, growth factors, and other natural mediators such as NO and PG on the development and biomechanical properties of the meniscus prostheses. Aim 4: Test the ability of the meniscus scaffold prosthesis to attach to bone and function in vivo. We will place the in vitro-generated meniscus prostheses into sites of fresh-ly resected medial menisci in dogs and leave the prostheses in place for up to 12 weeks, after which we will evaluate their function and their effects on development of pathology in the joint. Our work will have a direct effect on veterans with meniscal injuries, facilitating a more rapid recovery and reducing long term morbidity. Also, for active-duty military personnel, it may result in more rapid return to active duty. PUBLIC HEALTH RELEVANCE: Project narrative Relevance of the proposed work to United States public health and the VA patient care mission: Many veterans have meniscal injuries and tears. Meniscal injuries may be secondary to overt trauma, or in other cases, meniscal pathology may reflect alterations in knee joint function in association with aging, osteoarthritis, rheumatoid arthritis, or gait disturbances. There are increasing numbers of young veterans from the recent years (especially the OIF/OEF veterans) who are requiring VA medical care and who have orthopedic injuries. Of the 144,424 OIF/OEF veterans who had used VA services in 2004, 57,570 (40%) were diagnosed with "Diseases of the Musculoskeletal System/Connective System" (ICD-Categories 710- 739). A large number of these were meniscal problems. A normal meniscus is critical for a normally functioning knee joint, and meniscal pathology frequently leads to overt osteoarthritis and its associated morbidity. Obesity is very common, and the increased joint and meniscal mechanical stress associated with obesity further enhances meniscal pathologic responses and pathology. Our attempts to methodically develop a good meniscal prosthesis based on novel scaffold and stem cell technology will be very important in making progress toward effective replacement of damaged menisci and avoidance of subsequent OA. Accomplishing the aims of this project will not only help in the production of an effective meniscus prosthesis, but it will also provide new information regarding the roles of inflammatory mediators in modulating normal and prosthetic meniscal performance. Our work will have a direct effect on veterans with meniscal injuries, facilitating a more rapid recovery and reducing long term morbidity. Also, for active-duty military personnel, it may result in fewer injury-related discharges and more frequent and rapid return to active duty.